In the past a tremendous amount of work has been devoted to the development of catalytically active particles, for many different processes. There has also been a considerable effort to try to understand the advantages and sometimes disadvantages of effects of shape when deviating from conventional shapes such as pellets, rods, spheres and cylinders for use in catalytic as well as non-catalytic duties.
Examples of known shapes are cloverleafs, dumbbells and C-shaped particles and “polylobal”-shaped particles including TL (Trilobe) or QL (Quadrulobe) form. They serve as alternatives to the conventional cylindrical shape and often provide advantages because of their increased surface-to-volume ratio which enables the exposure of more catalytic sites.
Various documents, such as U.S. Pat. No. 4,645,754, WO 0207882, EP 1108470 and WO 04014549 have described the use of catalyst support in the shape of rings.
The Fischer-Tropsch process can be used for the conversion of hydrocarbonaceous feed stocks into liquid and/or solid hydrocarbons. The feed stock (e.g. natural gas, associated gas and/or coal-bed methane, coal) is converted in a first step into a mixture of hydrogen and carbon monoxide (this mixture is often referred to as synthesis gas or syngas). The synthesis gas is then converted in one or more steps over a suitable catalyst at elevated temperature and pressure into hydrocarbons, such as paraffinic compounds, ranging from methane to high molecular weight molecules comprising up to 200 carbon atoms, or, under particular circumstances, even more.
Numerous types of reactor systems have been developed for carrying out the Fischer-Tropsch reaction. For example, Fischer-Tropsch reactor systems include fixed bed reactors, especially multi tubular fixed bed reactors, fluidised bed reactors, such as entrained fluidised bed reactors and fixed fluidised bed reactors, and slurry bed reactors such as three-phase slurry bubble columns and ebulated bed reactors.